I've long been skeptical of the theory that global warming is man-made. More accurately, I've long been skeptical of the evidence. The theory itself seems reasonable. We live in what is essentially a very, very big greenhouse. The temperature of the air we breathe is determined in part by the mix of gasses present in our atmosphere. Water vapor traps a lot of heat, as does methane, and, to a much smaller degree, carbon dioxide. We live in an era when modern life is changing the ratio of all of these gasses. We are liberating carbon that has long been trapped beneath the surface. Our modern agriculture has specialized in producing animals that produce a lot of methane. And even water vapor has new outlets into the atmosphere thanks to human activity, as anyone who has ever driven past a factory belching steam must surely have noticed. A lot of that water is taken from ancient aquifers far below ground, with molecules that haven't had a shot at the sky for millions of years,
But, of course, nothing is simple. Sure, our livestock farts out a lot of methane, but so did bisons and passenger pigeons, and we turned off those spigots. We may pull a lot of carbon out of the ground as coal and oil, but we take a lot of carbon out of the atmosphere by cutting down forests to build houses and print books. The new forests that grow in the wake of our activities pull a lot of carbon out of the air. As for water vapor, there is so much water in the atmosphere that human actions can barely be measured.
As for whether the world is getting warmer, I think that's pretty well established. There's a long set of non-biased data that point to a fairly consistent warming trend, at least in the northern hemisphere, dating back to the 1850s. But, of course, this follows a centuries long cooling trend known as the "Little Ice Age." The problem with figuring out if human actions lead to climate change is that there is no such thing as climate stability. Our present warming trend could just be part of the background variation inherent in our climate.
But, perhaps because some global warming proponents are seizing on our current heat wave as evidence of man made climate change, I've noticed some skeptics adopting some of the same religious ferver they denounce in their opponents. The other day, I read an article talking about how all the various climate models on computers had been debunked. If the computers got it wrong, there's no man-made climate change! None! But, that argument is a false one if you give it even half a moments thought. The reality of changing climate has nothing at all to do with the existence of good computer models. The mastodons didn't look once at a chart showing the ice age might be coming to an end, but it ended anyway. Just because we can't model the effects of human activity upon the atmosphere isn't evidence that there aren't any such effects.
I think skepticism is healthy. Being skeptical of your own skepticism isn't a bad thing either. It's easy to argue against man-made global warming just for the satisfaction of poking holes in the near religious certainty of the proponents. The sky-is-falling doomsday predictions are fun to shoot down. But, don't lose sight of a simple truth: Natural variation might explain all the climate change we've experienced in recent centuries. But, it's also just as valid to argue that natural variation might mask genuine long term harm we're inflicting upon the earth by tweaking the atmosphere a little more each year. Cool-headed, reasoned certainty that man isn't causing long term climate change seems to me to be just as foolish a position as feverish certainty that we are.
If I may use a few analogies, climate change alarmists may be Chicken-Littles, panicking over a random string of hot days. But climate change skeptics might be the proverbial frog in the pot of water, never taking action to save themselves as the temp climbs slowly to boiling.